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Yong J, Johnson JD, Arvan P, Han J, Kaufman RJ. Therapeutic opportunities for pancreatic β-cell ER stress in diabetes mellitus. Nat Rev Endocrinol 2021; 17:455-467. [PMID: 34163039 PMCID: PMC8765009 DOI: 10.1038/s41574-021-00510-4] [Citation(s) in RCA: 86] [Impact Index Per Article: 28.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 05/06/2021] [Indexed: 02/06/2023]
Abstract
Diabetes mellitus is characterized by the failure of insulin-secreting pancreatic β-cells (or β-cell death) due to either autoimmunity (type 1 diabetes mellitus) or failure to compensate for insulin resistance (type 2 diabetes mellitus; T2DM). In addition, mutations of critical genes cause monogenic diabetes. The endoplasmic reticulum (ER) is the primary site for proinsulin folding; therefore, ER proteostasis is crucial for both β-cell function and survival under physiological and pathophysiological challenges. Importantly, the ER is also the major intracellular Ca2+ storage organelle, generating Ca2+ signals that contribute to insulin secretion. ER stress is associated with the pathogenesis of diabetes mellitus. In this Review, we summarize the mutations in monogenic diabetes that play causal roles in promoting ER stress in β-cells. Furthermore, we discuss the possible mechanisms responsible for ER proteostasis imbalance with a focus on T2DM, in which both genetics and environment are considered important in promoting ER stress in β-cells. We also suggest that controlled insulin secretion from β-cells might reduce the progression of a key aspect of the metabolic syndrome, namely nonalcoholic fatty liver disease. Finally, we evaluate potential therapeutic approaches to treat T2DM, including the optimization and protection of functional β-cell mass in individuals with T2DM.
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Affiliation(s)
- Jing Yong
- Degenerative Diseases Program, Sanford-Burnham-Prebys Medical Discovery Institute, La Jolla, CA, USA
| | - James D Johnson
- Department of Cellular and Physiological Sciences & Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Peter Arvan
- Division of Metabolism Endocrinology & Diabetes, University of Michigan Medical Center, Ann Arbor, MI, USA
| | - Jaeseok Han
- Soonchunhyang Institute of Medi-bio Science (SIMS), Soonchunhyang University, Cheonan-si, Choongchungnam-do, Republic of Korea.
| | - Randal J Kaufman
- Degenerative Diseases Program, Sanford-Burnham-Prebys Medical Discovery Institute, La Jolla, CA, USA.
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Szwergold B. A Hypothesis: Fructosamine-3-Kinase-Related-Protein (FN3KRP) Catalyzes Deglycation of Maillard Intermediates Directly Downstream from Fructosamines. Rejuvenation Res 2021; 24:310-318. [PMID: 34314247 DOI: 10.1089/rej.2021.0009] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Non-enzymatic glycation (a.k.a. Maillard reaction) is a series of random spontaneous reactions between reducing sugars and amines, resulting in the formation of irreversible advanced glycation endproducts (AGE's). In food chemistry, this process is beneficial by contributing to the flavor, aroma, texture, and appearance of cooked foods. In vivo, however, Maillard reaction is deleterious because uncontrolled modification and crosslinking of biological macromolecules impairs their function. Consequently, chronic hyperglycemia of diabetes mellitus, for instance, leads to increased non-enzymatic glycation and diverse, multi-organ pathologies of diabetic complications. Based on the fact that toxic compounds, such as free radicals, are detoxified in vivo by specific defense mechanisms, one would expect to find mechanisms to control glucose toxicity as well. Thus far, only one such enzyme, fructosamine-3-kinase (FN3K), has been characterized. It operates intracellularly by catalyzing ATP-dependent removal of Maillard adducts, D-fructoselysines, from proteins, thereby reducing the Maillard reaction flux from glucose to AGE's. When FN3K was isolated, a closely related but distinct protein copurified with it. Unlike FN3K, however, this enzyme, fructosamine-3-kinase-related protein (FN3KRP), does not phosphorylate D-fructoselysines but it does phosphorylate several other (non-physiological) substrates. Interestingly, the distribution of FN3KRP in nature appears to be nearly universal whereas that of FN3K is limited to endotherms. In this article, it is suggested that the function of FN3KRP is deglycation of Maillard adducts downstream from fructoselysines. Such a mechanism, if proven correct, would be valuable given reports on apparent correlations between FN3KRP and some chronic conditions and/or diseases, such as a recent publication which proposes that the FN3KRP gene may be a longevity gene.
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Beeraka NM, Bovilla VR, Doreswamy SH, Puttalingaiah S, Srinivasan A, Madhunapantula SV. The Taming of Nuclear Factor Erythroid-2-Related Factor-2 (Nrf2) Deglycation by Fructosamine-3-Kinase (FN3K)-Inhibitors-A Novel Strategy to Combat Cancers. Cancers (Basel) 2021; 13:cancers13020281. [PMID: 33466626 PMCID: PMC7828646 DOI: 10.3390/cancers13020281] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Revised: 01/06/2021] [Accepted: 01/07/2021] [Indexed: 02/06/2023] Open
Abstract
Simple Summary Aim of this review is to provide an overview on (a) Fructosamine-3-Kinase (FN3K) and its role in regulating Nuclear Factor Erythorid-2-Related Factor-2 (Nrf2); (b) the role of glycation and deglycation mechanisms in modulating the functional properties of proteins, in particular, the Nrf2; (c) the dual role of Nrf2 in the prevention and treatment of cancers. Since controlling the glycation of Nrf2 is one of the key mechanisms determining the fate of a cell; whether to get transformed into a cancerous one or to stay as a normal one, it is important to regulate Nrf2 and deglycating FN3K using pharmacological agents. Inhibitors of FN3K are being explored currently to modulate Nrf2 activity thereby control the cancers. Abstract Glycated stress is mediated by the advanced glycation end products (AGE) and the binding of AGEs to the receptors for advanced glycation end products (RAGEs) in cancer cells. RAGEs are involved in mediating tumorigenesis of multiple cancers through the modulation of several downstream signaling cascades. Glycated stress modulates various signaling pathways that include p38 mitogen-activated protein kinase (p38 MAPK), nuclear factor kappa–B (NF-κB), tumor necrosis factor (TNF)-α, etc., which further foster the uncontrolled proliferation, growth, metastasis, angiogenesis, drug resistance, and evasion of apoptosis in several cancers. In this review, a balanced overview on the role of glycation and deglycation in modulating several signaling cascades that are involved in the progression of cancers was discussed. Further, we have highlighted the functional role of deglycating enzyme fructosamine-3-kinase (FN3K) on Nrf2-driven cancers. The activity of FN3K is attributed to its ability to deglycate Nrf2, a master regulator of oxidative stress in cells. FN3K is a unique protein that mediates deglycation by phosphorylating basic amino acids lysine and arginine in various proteins such as Nrf2. Deglycated Nrf2 is stable and binds to small musculoaponeurotic fibrosarcoma (sMAF) proteins, thereby activating cellular antioxidant mechanisms to protect cells from oxidative stress. This cellular protection offered by Nrf2 activation, in one way, prevents the transformation of a normal cell into a cancer cell; however, in the other way, it helps a cancer cell not only to survive under hypoxic conditions but also, to stay protected from various chemo- and radio-therapeutic treatments. Therefore, the activation of Nrf2 is similar to a double-edged sword and, if not controlled properly, can lead to the development of many solid tumors. Hence, there is a need to develop novel small molecule modulators/phytochemicals that can regulate FN3K activity, thereby maintaining Nrf2 in a controlled activation state.
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Affiliation(s)
- Narasimha M. Beeraka
- Center of Excellence in Molecular Biology and Regenerative Medicine (CEMR), Department of Biochemistry, JSS Medical College, JSS Academy of Higher Education & Research (JSS AHER), Mysuru, Karnataka 570015, India; (N.M.B.); (V.R.B.); (S.H.D.); (S.P.)
| | - Venugopal R. Bovilla
- Center of Excellence in Molecular Biology and Regenerative Medicine (CEMR), Department of Biochemistry, JSS Medical College, JSS Academy of Higher Education & Research (JSS AHER), Mysuru, Karnataka 570015, India; (N.M.B.); (V.R.B.); (S.H.D.); (S.P.)
- Public Health Research Institute of India (PHRII), Mysuru, Karnataka 570020, India
| | - Shalini H. Doreswamy
- Center of Excellence in Molecular Biology and Regenerative Medicine (CEMR), Department of Biochemistry, JSS Medical College, JSS Academy of Higher Education & Research (JSS AHER), Mysuru, Karnataka 570015, India; (N.M.B.); (V.R.B.); (S.H.D.); (S.P.)
| | - Sujatha Puttalingaiah
- Center of Excellence in Molecular Biology and Regenerative Medicine (CEMR), Department of Biochemistry, JSS Medical College, JSS Academy of Higher Education & Research (JSS AHER), Mysuru, Karnataka 570015, India; (N.M.B.); (V.R.B.); (S.H.D.); (S.P.)
| | - Asha Srinivasan
- Division of Nanoscience and Technology, Faculty of Life Sciences, JSS Academy of Higher Education & Research (JSS AHER), Mysuru, Karnataka 570015, India;
| | - SubbaRao V. Madhunapantula
- Center of Excellence in Molecular Biology and Regenerative Medicine (CEMR), Department of Biochemistry, JSS Medical College, JSS Academy of Higher Education & Research (JSS AHER), Mysuru, Karnataka 570015, India; (N.M.B.); (V.R.B.); (S.H.D.); (S.P.)
- Special Interest Group in Cancer Biology and Cancer Stem Cells, JSS Medical College, JSS Academy of Higher Education & Research (JSS AHER), Mysuru, Karnataka 570015, India
- Correspondence: ; Tel.: +91-810-527-8621
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Shrestha S, Katiyar S, Sanz-Rodriguez CE, Kemppinen NR, Kim HW, Kadirvelraj R, Panagos C, Keyhaninejad N, Colonna M, Chopra P, Byrne DP, Boons GJ, van der Knaap E, Eyers PA, Edison AS, Wood ZA, Kannan N. A redox-active switch in fructosamine-3-kinases expands the regulatory repertoire of the protein kinase superfamily. Sci Signal 2020; 13:13/639/eaax6313. [PMID: 32636308 DOI: 10.1126/scisignal.aax6313] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Aberrant regulation of metabolic kinases by altered redox homeostasis substantially contributes to aging and various diseases, such as diabetes. We found that the catalytic activity of a conserved family of fructosamine-3-kinases (FN3Ks), which are evolutionarily related to eukaryotic protein kinases, is regulated by redox-sensitive cysteine residues in the kinase domain. The crystal structure of the FN3K homolog from Arabidopsis thaliana revealed that it forms an unexpected strand-exchange dimer in which the ATP-binding P-loop and adjoining β strands are swapped between two chains in the dimer. This dimeric configuration is characterized by strained interchain disulfide bonds that stabilize the P-loop in an extended conformation. Mutational analysis and solution studies confirmed that the strained disulfides function as redox "switches" to reversibly regulate the activity and dimerization of FN3K. Human FN3K, which contains an equivalent P-loop Cys, was also redox sensitive, whereas ancestral bacterial FN3K homologs, which lack a P-loop Cys, were not. Furthermore, CRISPR-mediated knockout of FN3K in human liver cancer cells altered the abundance of redox metabolites, including an increase in glutathione. We propose that redox regulation evolved in FN3K homologs in response to changing cellular redox conditions. Our findings provide insights into the origin and evolution of redox regulation in the protein kinase superfamily and may open new avenues for targeting human FN3K in diabetic complications.
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Affiliation(s)
- Safal Shrestha
- Institute of Bioinformatics, University of Georgia, Athens, GA 30602, USA
| | - Samiksha Katiyar
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA
| | - Carlos E Sanz-Rodriguez
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA
| | - Nolan R Kemppinen
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA
| | - Hyun W Kim
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA
| | - Renuka Kadirvelraj
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA
| | - Charalampos Panagos
- Complex Carbohydrate Research Center (CCRC), University of Georgia, Athens, GA 30602, USA
| | - Neda Keyhaninejad
- Center for Applied Genetic Technologies (CAGT), University of Georgia, Athens, GA 30602, USA
| | - Maxwell Colonna
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA.,Complex Carbohydrate Research Center (CCRC), University of Georgia, Athens, GA 30602, USA
| | - Pradeep Chopra
- Complex Carbohydrate Research Center (CCRC), University of Georgia, Athens, GA 30602, USA
| | - Dominic P Byrne
- Department of Biochemistry, Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK
| | - Geert J Boons
- Complex Carbohydrate Research Center (CCRC), University of Georgia, Athens, GA 30602, USA.,Department of Chemical Biology and Drug Discovery, Utrecht Institute for Pharmaceutical Sciences, and Bijvoet Center for Biomolecular Research, Utrecht University, 3584 CG Utrecht, Netherlands
| | - Esther van der Knaap
- Center for Applied Genetic Technologies (CAGT), University of Georgia, Athens, GA 30602, USA.,Department of Horticulture, University of Georgia, Athens, GA 30602, USA.,Institute of Plant Breeding, Genetics and Genomics, University of Georgia, Athens, GA 30602, USA
| | - Patrick A Eyers
- Department of Biochemistry, Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK
| | - Arthur S Edison
- Institute of Bioinformatics, University of Georgia, Athens, GA 30602, USA.,Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA.,Complex Carbohydrate Research Center (CCRC), University of Georgia, Athens, GA 30602, USA
| | - Zachary A Wood
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA
| | - Natarajan Kannan
- Institute of Bioinformatics, University of Georgia, Athens, GA 30602, USA. .,Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA
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5
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Bensellam M, Jonas JC, Laybutt DR. Mechanisms of β-cell dedifferentiation in diabetes: recent findings and future research directions. J Endocrinol 2018; 236:R109-R143. [PMID: 29203573 DOI: 10.1530/joe-17-0516] [Citation(s) in RCA: 139] [Impact Index Per Article: 23.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Accepted: 12/04/2017] [Indexed: 12/13/2022]
Abstract
Like all the cells of an organism, pancreatic β-cells originate from embryonic stem cells through a complex cellular process termed differentiation. Differentiation involves the coordinated and tightly controlled activation/repression of specific effectors and gene clusters in a time-dependent fashion thereby giving rise to particular morphological and functional cellular features. Interestingly, cellular differentiation is not a unidirectional process. Indeed, growing evidence suggests that under certain conditions, mature β-cells can lose, to various degrees, their differentiated phenotype and cellular identity and regress to a less differentiated or a precursor-like state. This concept is termed dedifferentiation and has been proposed, besides cell death, as a contributing factor to the loss of functional β-cell mass in diabetes. β-cell dedifferentiation involves: (1) the downregulation of β-cell-enriched genes, including key transcription factors, insulin, glucose metabolism genes, protein processing and secretory pathway genes; (2) the concomitant upregulation of genes suppressed or expressed at very low levels in normal β-cells, the β-cell forbidden genes; and (3) the likely upregulation of progenitor cell genes. These alterations lead to phenotypic reconfiguration of β-cells and ultimately defective insulin secretion. While the major role of glucotoxicity in β-cell dedifferentiation is well established, the precise mechanisms involved are still under investigation. This review highlights the identified molecular mechanisms implicated in β-cell dedifferentiation including oxidative stress, endoplasmic reticulum (ER) stress, inflammation and hypoxia. It discusses the role of Foxo1, Myc and inhibitor of differentiation proteins and underscores the emerging role of non-coding RNAs. Finally, it proposes a novel hypothesis of β-cell dedifferentiation as a potential adaptive mechanism to escape cell death under stress conditions.
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Affiliation(s)
- Mohammed Bensellam
- Garvan Institute of Medical ResearchSydney, New South Wales, Australia
- Université Catholique de LouvainInstitut de Recherche Expérimentale et Clinique, Pôle d'Endocrinologie, Diabète et Nutrition, Brussels, Belgium
| | - Jean-Christophe Jonas
- Université Catholique de LouvainInstitut de Recherche Expérimentale et Clinique, Pôle d'Endocrinologie, Diabète et Nutrition, Brussels, Belgium
| | - D Ross Laybutt
- Garvan Institute of Medical ResearchSydney, New South Wales, Australia
- St Vincent's Clinical SchoolUNSW Sydney, Sydney, New South Wales, Australia
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Szwergold B. A Hypothesis: Moderate Consumption of Alcohol Contributes to Lower Prevalence of Type 2 Diabetes Due to the Scavenging of Alpha-Dicarbonyls by Dietary Polyphenols. Rejuvenation Res 2017; 21:389-404. [PMID: 28891383 DOI: 10.1089/rej.2017.1974] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The world is experiencing an epidemic of type-2-diabetes mellitus (T2DM). This has led to increased morbidity and mortality, explosive growth in health care budgets, and an even greater adverse, if indirect, impact on societies and economies of affected countries. While genetic susceptibility to T2DM is a major determinant of its prevalence, changes in lifestyles also play a role. One such change has been a transition from traditional diets characterized by low caloric and high nutrient density to calorie-rich but nutrient-poor Western diets. Given this, one solution to the epidemic of T2DM would be to abandon Western diets and revert to traditional eating patterns. However, traditional diets cannot provide enough calories for the increasing global population, so transition from traditional to Western foodstuffs appears to be irreversible. Consequently, the only practical solution to problems caused by these changes is to modify Western diets, possibly by supplementing them with functional foods containing nutrients that would compensate for these dietary deficits. I present in this study a hypothesis to explain why shifts from traditional to Western diets have been so problematic and to suggest nutrients that may counteract these adverse effects. I postulate that the components of traditional diets that may compensate for deficiencies of Westerns diets are scavengers of reactive α-dicarbonyls produced as unavoidable by-products of glucose and lipid metabolism. Most important among these scavengers are some plant secondary metabolites: polyphenols, phlorotannins, and carotenoids. They are found in alcoholic beverages and are abundant in seasonings, cocoa, coffee, tea, whole grains, pigmented vegetables, fruits, and berries.
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7
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de Souza AH, Santos LRB, Roma LP, Bensellam M, Carpinelli AR, Jonas JC. NADPH oxidase-2 does not contribute to β-cell glucotoxicity in cultured pancreatic islets from C57BL/6J mice. Mol Cell Endocrinol 2017; 439:354-362. [PMID: 27664519 DOI: 10.1016/j.mce.2016.09.022] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Revised: 08/24/2016] [Accepted: 09/20/2016] [Indexed: 11/20/2022]
Abstract
High glucose-induced oxidative stress and increased NADPH oxidase-2 (NOX2) activity may contribute to the progressive decline of the functional β-cell mass in type 2 diabetes. To test that hypothesis, we characterized, in islets from male NOX2 knockout (NOX2-KO) and wild-type (WT) C57BL/6J mice cultured for up to 3 weeks at 10 or 30 mmol/l glucose (G10 or G30), the in vitro effects of glucose on cytosolic oxidative stress using probes sensing glutathione oxidation (GRX1-roGFP2), thiol oxidation (roGFP1) or H2O2 (roGFP2-Orp1), on β-cell stimulus-secretion coupling events and on β-cell apoptosis. After 1-2 days of culture in G10, the glucose stimulation of insulin secretion (GSIS) was ∼1.7-fold higher in NOX2-KO vs. WT islets at 20-30 mmol/l glucose despite similar rises in NAD(P)H and intracellular calcium concentration ([Ca2+]i) and no differences in cytosolic GRX1-roGFP2 oxidation. After long-term culture at G10, roGFP1 and roGFP2-Orp1 oxidation and β-cell apoptosis remained low, and the glucose-induced rises in NAD(P)H, [Ca2+]i and GSIS were similarly preserved in both islet types. After prolonged culture at G30, roGFP1 and roGFP2-Orp1 oxidation increased in parallel with β-cell apoptosis, the glucose sensitivity of the NADPH, [Ca2+]i and insulin secretion responses increased, the maximal [Ca2+]i response decreased, but maximal GSIS was preserved. These responses were almost identical in both islet types. In conclusion, NOX2 is a negative regulator of maximal GSIS in C57BL/6J mouse islets, but it does not detectably contribute to the in vitro glucotoxic induction of cytosolic oxidative stress and alterations of β-cell survival and function.
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Affiliation(s)
- Arnaldo H de Souza
- Université catholique de Louvain, Institute of Experimental and Clinical Research, Pole of Endocrinology, Diabetes and Nutrition, Brussels, Belgium; Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Laila R B Santos
- Université catholique de Louvain, Institute of Experimental and Clinical Research, Pole of Endocrinology, Diabetes and Nutrition, Brussels, Belgium
| | - Leticia P Roma
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Mohammed Bensellam
- Université catholique de Louvain, Institute of Experimental and Clinical Research, Pole of Endocrinology, Diabetes and Nutrition, Brussels, Belgium
| | - Angelo R Carpinelli
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Jean-Christophe Jonas
- Université catholique de Louvain, Institute of Experimental and Clinical Research, Pole of Endocrinology, Diabetes and Nutrition, Brussels, Belgium.
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8
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Roma LP, Duprez J, Jonas JC. Glucokinase activation is beneficial or toxic to cultured rat pancreatic islets depending on the prevailing glucose concentration. Am J Physiol Endocrinol Metab 2015; 309:E632-9. [PMID: 26264555 DOI: 10.1152/ajpendo.00154.2015] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 08/10/2015] [Indexed: 11/22/2022]
Abstract
In rat pancreatic islets, β-cell gene expression, survival, and subsequent acute glucose stimulation of insulin secretion (GSIS) are optimally preserved by prolonged culture at 10 mM glucose (G10) and markedly altered by culture at G5 or G30. Here, we tested whether pharmacological glucokinase (GK) activation prevents these alterations during culture or improves GSIS after culture. Rat pancreatic islets were cultured 1-7 days at G5, G10, or G30 with or without 3 μM of the GK activator Ro 28-0450 (Ro). After culture, β-cell apoptosis and islet gene mRNA levels were measured, and the acute glucose-induced increase in NAD(P)H autofluorescence, intracellular calcium concentration, and insulin secretion were tested in the absence or presence of Ro. Prolonged culture of rat islets at G5 or G30 instead of G10 triggered β-cell apoptosis and reduced their glucose responsiveness. Addition of Ro during culture differently affected β-cell survival and glucose responsiveness depending on the glucose concentration during culture: it was beneficial to β-cell survival and function at G5, detrimental at G10, and ineffective at G30. In contrast, acute GK activation with Ro increased the glucose sensitivity of islets cultured at G10 but failed at restoring β-cell glucose responsiveness after culture at G5 or G30. We conclude that pharmacological GK activation prevents the alteration of β-cell survival and function by long-term culture at G5 but mimics glucotoxicity when added to G10. The complex effects of glucose on the β-cell phenotype result from changes in glucose metabolism and not from an effect of glucose per se.
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Affiliation(s)
- Leticia P Roma
- Université catholique de Louvain, Institut de recherche expérimentale et clinique, Pôle d'endocrinologie, diabète et nutrition, Brussels, Belgium; and
| | - Jessica Duprez
- Université catholique de Louvain, Institut de recherche expérimentale et clinique, Pôle d'endocrinologie, diabète et nutrition, Brussels, Belgium; and
| | - Jean-Christophe Jonas
- Université catholique de Louvain, Institut de recherche expérimentale et clinique, Pôle d'endocrinologie, diabète et nutrition, Brussels, Belgium; and Fonds de la recherche scientifique-FNRS, Brussels, Belgium
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9
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Chae H, Gilon P. Can Tea Extracts Exert a Protective Effect Against Diabetes by Reducing Oxidative Stress and Decreasing Glucotoxicity in Pancreatic β-Cells? Diabetes Metab J 2015; 39:27-30. [PMID: 25729709 PMCID: PMC4342533 DOI: 10.4093/dmj.2015.39.1.27] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Affiliation(s)
- Heeyoung Chae
- Pôle d'Endocrinologie, Diabète et Nutrition, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, Brussels, Belgium
| | - Patrick Gilon
- Pôle d'Endocrinologie, Diabète et Nutrition, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, Brussels, Belgium
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10
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Jaisson S, Gillery P. Impaired proteostasis: role in the pathogenesis of diabetes mellitus. Diabetologia 2014; 57:1517-27. [PMID: 24816368 DOI: 10.1007/s00125-014-3257-1] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Accepted: 04/08/2014] [Indexed: 01/06/2023]
Abstract
In living organisms, proteins are regularly exposed to 'molecular ageing', which corresponds to a set of non-enzymatic modifications that progressively cause irreversible damage to proteins. This phenomenon is greatly amplified under pathological conditions, such as diabetes mellitus. For their survival and optimal functioning, cells have to maintain protein homeostasis, also called 'proteostasis'. This process acts to maintain a high proportion of functional and undamaged proteins. Different mechanisms are involved in proteostasis, among them degradation systems (the main intracellular proteolytic systems being proteasome and lysosomes), folding systems (including molecular chaperones), and enzymatic mechanisms of protein repair. There is growing evidence that the disruption of proteostasis may constitute a determining event in pathophysiology. The aim of this review is to demonstrate how such a dysregulation may be involved in the pathogenesis of diabetes mellitus and in the onset of its long-term complications.
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Affiliation(s)
- Stéphane Jaisson
- Laboratory of Medical Biochemistry and Molecular Biology, University of Reims Champagne Ardenne, Reims, France,
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11
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Aldini G, Vistoli G, Stefek M, Chondrogianni N, Grune T, Sereikaite J, Sadowska-Bartosz I, Bartosz G. Molecular strategies to prevent, inhibit, and degrade advanced glycoxidation and advanced lipoxidation end products. Free Radic Res 2013; 47 Suppl 1:93-137. [PMID: 23560617 DOI: 10.3109/10715762.2013.792926] [Citation(s) in RCA: 111] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The advanced glycoxidation end products (AGEs) and lipoxidation end products (ALEs) contribute to the development of diabetic complications and of other pathologies. The review discusses the possibilities of counteracting the formation and stimulating the degradation of these species by pharmaceuticals and natural compounds. The review discusses inhibitors of ALE and AGE formation, cross-link breakers, ALE/AGE elimination by enzymes and proteolytic systems, receptors for advanced glycation end products (RAGEs) and blockade of the ligand-RAGE axis.
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Affiliation(s)
- Giancarlo Aldini
- Department of Pharmaceutical Sciences, University of Milan, Milan, Italy
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12
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Bensellam M, Laybutt DR, Jonas JC. The molecular mechanisms of pancreatic β-cell glucotoxicity: recent findings and future research directions. Mol Cell Endocrinol 2012; 364:1-27. [PMID: 22885162 DOI: 10.1016/j.mce.2012.08.003] [Citation(s) in RCA: 206] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Revised: 07/11/2012] [Accepted: 08/01/2012] [Indexed: 02/06/2023]
Abstract
It is well established that regular physiological stimulation by glucose plays a crucial role in the maintenance of the β-cell differentiated phenotype. In contrast, prolonged or repeated exposure to elevated glucose concentrations both in vitro and in vivo exerts deleterious or toxic effects on the β-cell phenotype, a concept termed as glucotoxicity. Evidence indicates that the latter may greatly contribute to the pathogenesis of type 2 diabetes. Through the activation of several mechanisms and signaling pathways, high glucose levels exert deleterious effects on β-cell function and survival and thereby, lead to the worsening of the disease over time. While the role of high glucose-induced β-cell overstimulation, oxidative stress, excessive Unfolded Protein Response (UPR) activation, and loss of differentiation in the alteration of the β-cell phenotype is well ascertained, at least in vitro and in animal models of type 2 diabetes, the role of other mechanisms such as inflammation, O-GlcNacylation, PKC activation, and amyloidogenesis requires further confirmation. On the other hand, protein glycation is an emerging mechanism that may play an important role in the glucotoxic deterioration of the β-cell phenotype. Finally, our recent evidence suggests that hypoxia may also be a new mechanism of β-cell glucotoxicity. Deciphering these molecular mechanisms of β-cell glucotoxicity is a mandatory first step toward the development of therapeutic strategies to protect β-cells and improve the functional β-cell mass in type 2 diabetes.
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Affiliation(s)
- Mohammed Bensellam
- Université catholique de Louvain, Institut de recherche expérimentale et clinique, Pôle d'endocrinologie, diabète et nutrition, Brussels, Belgium
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Roma LP, Pascal SM, Duprez J, Jonas JC. Mitochondrial oxidative stress contributes differently to rat pancreatic islet cell apoptosis and insulin secretory defects after prolonged culture in a low non-stimulating glucose concentration. Diabetologia 2012; 55:2226-37. [PMID: 22643931 DOI: 10.1007/s00125-012-2581-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/25/2011] [Accepted: 04/19/2012] [Indexed: 01/14/2023]
Abstract
AIMS/HYPOTHESIS Pancreatic beta cells chronically exposed to low glucose concentrations show signs of oxidative stress, loss of glucose-stimulated insulin secretion (GSIS) and increased apoptosis. Our aim was to confirm the role of mitochondrial oxidative stress in rat islet cell apoptosis under these culture conditions and to evaluate whether its reduction similarly improves survival and GSIS. METHODS Apoptosis, oxidative stress-response gene mRNA expression and glucose-induced stimulation of mitochondrial metabolism, intracellular Ca(2+) concentration and insulin secretion were measured in male Wistar rat islets cultured for 1 week in RPMI medium containing 5-10 mmol/l glucose with or without manganese(III)tetrakis(4-benzoic acid)porphyrin (MnTBAP) or N-acetyl-L-: cysteine (NAC). Oxidative stress was measured in islet cell clusters cultured under similar conditions using cytosolic and mitochondrial redox-sensitive green fluorescent protein (roGFP1/mt-roGFP1). RESULTS Prolonged culture in 5 vs 10 mmol/l glucose increased mt-roGFP1 (but not roGFP1) oxidation followed by beta cell apoptosis and loss of GSIS resulting from reduced insulin content, mitochondrial metabolism, Ca(2+) influx and Ca(2+)-induced secretion. Tolbutamide-induced, but not high K(+)-induced, Ca(2+) influx was also suppressed. Under these conditions, MnTBAP, but not NAC, triggered parallel ~50-70% reductions in mt-roGFP1 oxidation and beta cell apoptosis, but failed to protect against the loss of GSIS despite significant improvement in glucose-induced and tolbutamide-induced Ca(2+) influx. CONCLUSIONS/INTERPRETATION Mitochondrial oxidative stress contributes differently to rat pancreatic islet cell apoptosis and insulin secretory defects during culture in a low glucose concentration. Thus, targeting beta cell survival may not be sufficient to restore insulin secretion when beta cells suffer from prolonged mitochondrial oxidative stress, e.g. in the context of reduced glucose metabolism.
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Affiliation(s)
- L P Roma
- Université catholique de Louvain, Institut de recherche expérimentale et clinique, Pôle d'endocrinologie, diabète et nutrition, Avenue Hippocrate 55, B1.55.06, 1200, Brussels, Belgium
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Wei Y, Han CS, Zhou J, Liu Y, Chen L, He RQ. d-ribose in glycation and protein aggregation. Biochim Biophys Acta Gen Subj 2012; 1820:488-94. [DOI: 10.1016/j.bbagen.2012.01.005] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2011] [Revised: 01/05/2012] [Accepted: 01/09/2012] [Indexed: 12/23/2022]
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Mosca L, Penco S, Patrosso MC, Marocchi A, Lapolla A, Sartore G, Chilelli NC, Paleari R, Mosca A. Genetic variability of the fructosamine 3-kinase gene in diabetic patients. Clin Chem Lab Med 2011; 49:803-8. [PMID: 21288167 DOI: 10.1515/cclm.2011.133] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND Nonenzymatic glycation appears to be an important factor in the pathogenesis of diabetic complications. Fructosamine 3-kinase (FN3K), initially identified in erythrocytes, appears to be responsible for the removal of fructosamine from proteins, suggesting a protective role in nonenzymatic glycation. Recently, genetic variants in the FN3K gene have been studied in diabetic patients. The aim of our study was the molecular characterization of the FN3K gene in a representative group of Italian patients with type 1 (T1DM) and 2 (T2DM) diabetes mellitus and in a cohort of healthy controls. METHODS Seventy diabetic subjects (35 type 1 and 35 type 2) with stable glycemic control and 33 healthy control subjects were evaluated using PCR and direct sequencing of the FN3K gene. Denaturing high performance liquid chromatography (DHPLC) was used in controls for screening for the presence of the genetic variants previously found in diabetic patients. RESULTS Seven different genetic variants were identified, five of them already reported and two new: the p.R187X and p.Y239C mutations identified in two females affected by T2DM. No significant association was found between certain polymorphisms and diabetes conditions. Preliminary haplotype studies are also reported. With respect to genotypes, we noted that some were not present in all the investigated cohort, and some were found related to higher glycated hemoglobin compared to others, although not at a significant level, probably because of the small number of subjects investigated. CONCLUSIONS In conclusion, this study identified two new mutations and additional variants within the FN3K gene. This is the first study on FN3K in Italy. Future work is needed to achieve a better understanding of the FN3K enzyme and its possible clinical utility in the management of diabetic patients.
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Affiliation(s)
- Lorena Mosca
- Laboratorio di Genetica Medica, Ospedale Niguarda Ca' Granda, Milano, Italy
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Van Schaftingen E, Collard F, Wiame E, Veiga-da-Cunha M. Enzymatic repair of Amadori products. Amino Acids 2010; 42:1143-50. [PMID: 20967558 DOI: 10.1007/s00726-010-0780-3] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2010] [Accepted: 08/22/2010] [Indexed: 11/25/2022]
Abstract
Protein deglycation, a new form of protein repair, involves several enzymes. Fructosamine-3-kinase (FN3K), an enzyme found in mammals and birds, phosphorylates fructosamines on the third carbon of their sugar moiety, making them unstable and causing them to detach from proteins. This enzyme acts particularly well on fructose-epsilon-lysine, both in free form and in the accessible regions of proteins. Mice deficient in FN3K accumulate protein-bound fructosamines and free fructoselysine, indicating that the deglycation mechanism initiated by FN3K is operative in vivo. Mammals and birds also have an enzyme designated 'FN3K-related protein' (FN3KRP), which shares ≈ 65% sequence identity with FN3K. Unlike FN3K, FN3KRP does not phosphorylate fructosamines, but acts on ribulosamines and erythrulosamines. As with FN3K, the third carbon is phosphorylated and this leads to destabilization of the ketoamines. Experiments with intact erythrocytes indicate that FN3KRP is also a protein-repair enzyme. Its physiological substrates are most likely formed from ribose 5-phosphate and erythrose 4-phosphate, which give rise to ketoamine 5- or 4-phosphates. The latter are dephosphorylated by 'low-molecular-weight protein-tyrosine-phosphatase-A' (LMW-PTP-A) before FN3KRP transfers a phosphate on the third carbon. The specificity of FN3K homologues present in plants and bacteria is similar to that of mammalian FN3KRP, suggesting that deglycation of ribulosamines and/or erythrulosamines is an ancient mechanism. Mammalian cells contain also a phosphatase acting on fructosamine 6-phosphates, which result from the reaction of proteins with glucose 6-phosphate.
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Affiliation(s)
- Emile Van Schaftingen
- de Duve Institute, Université catholique de Louvain, Avenue Hippocrate 75, B-1200, Brussels, Belgium.
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